This invention relates generally to the reinforcement of metals with fibers and, more particularly, to the preparation of composites of alumina fibers and aluminum.
Polycrystalline Al.sub.2 O.sub.3 fiber has long been considered ideal for reinforcing metals because of its high modulus and strength, chemical inertness and high temperature stability. Aluminum is ideally used in the aerospace, transportation and other industries because of its light weight, excellent corrosion resistance and low cost. It is the prime candidate for reinforcement with continuous polycrystalline .alpha.-Al.sub.2 O.sub.3 fibers prepared, for example, as described by Seufert in U.S. Pat. No. 3,808,015. The major problem limiting the utilization of Al.sub.2 O.sub.3 --Al composites has been the lack of a practical method to fabricate them due to the fact that aluminum does not adequately wet alumina.
Considerable effort has been expended in attempts to obtain wetting of the surface of Al.sub.2 O.sub.3 fibers with aluminum, for example, by coating the surface of Al.sub.2 O.sub.3 fibers with metals like Ni, Ti, Cu and the like. However, these metal coating methods are slow, expensive, difficult to scale up and sometimes yield composites with brittle interfaces. Brittle interfaces tend to lower the mechanical properties such as flexural and shear strengths.